1. Technical Field
The present invention relates to a piezoelectric element, a method for manufacturing a piezoelectric element, a piezoelectric actuator, a liquid ejecting head, and a liquid ejecting apparatus.
2. Related Art
A piezoelectric element is a device that has variable shape characteristics. When a voltage is applied thereto, its shape changes. In the structure of a piezoelectric element, a piezoelectric substance layer is sandwiched between electrodes. A piezoelectric element has a wide array of uses. For example, a piezoelectric element is provided in a liquid droplet discharging head of an ink-jet printer. A piezoelectric element is used for various actuators.
A piezoelectric substance layer that constitutes a part of a piezoelectric element is susceptible to external moisture. When affected by moisture, in some cases, the characteristics of the piezoelectric substance layer deteriorate. For ensuring sufficient moisture resistance of a piezoelectric substance layer, for example, a structure in which an upper electrode covers a piezoelectric substance layer has been proposed in the art. An example of such a structure is disclosed in JP-A-2005-88441. However, the related-art structure disclosed in JP-A-2005-88441 has the following disadvantage. Stress may concentrate at a part of an upper electrode (more specifically, at a region of an upper electrode in the neighborhood of a junction where the side surface of a piezoelectric substance layer meets with the upper surface of a substrate (vibrating plate, diaphragm)). As a result, in some cases, the part of the upper electrode where stress concentrates is destroyed, which makes it impossible to ensure sufficient moisture resistance of the piezoelectric substance layer.